Compilation
Blechnum attenuatum

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Name

Identification
Blechnum attenuatum (Sw.)Mett. [family PTERIDOPHYTA ]
Related name
  • Blechnum attenuatum

Flora

Entry for Blechnum attenuatum (Sw.) Mett. [family BLECHNACEAE]
Herbarium
Royal Botanic Gardens, Kew (K)
Collection
Flora of Tropical East Africa
Resource Type
Reference Sources
Entry From
Flora of Tropical East Africa, (2006) Author: B.S. PARRIS
Names
Blechnum attenuatum (Sw.) Mett. [family BLECHNACEAE], Fil. Hort. Bot. Lips.: 64, t. 3, fig. 1– 6 (1856); Tardieu-Blot in Mém. I.F.A.N. 28: 201, t. 39, fig. 7 (1953); F.W.T.A. ed. 2, Suppl.: 74 (1959); Tardieu-Blot, Fl. Madag., Polypod. 2: 8, fig. 2, 5– 7s (1960) & Fl. Cameroun 3: 295, t. 34, fig. 7 (1964); Schelpe in F.Z. Pterid.: 235 (1970) as var. attenuatum; Burrows, S. Afr. Ferns & Fern Allies: 326, fig. 330, t. 54, 4 (1990) as var. attenuatum; Iversen in Symb. Bot. Upsal. 29(3): 156 (1991); Johns, Pteridophytes T.E.A.: 98 (1991). Type: Mauritius, Groendal s.n. (P, holo.)
Onoclea attenuata Sw. [family WOODSIACEAE], in Schrad., J. Bot. 1800, 2: 73 (1801)
Information
Rhizomes 6– 40 mm in diameter including scales, ± erect to long-creeping; scales 12– 20≈ 1– 3 mm, linear-lanceolate, pale to dark chestnut-brown, sometimes with medium brown to blackish central stripe, sometimes crisped at apex. Stipes 5– 28≈ 0.2– 0.6 cm. Fronds pinnate or very deeply pinnately divided, fertile and sterile laminae similar in size, 23– 120(– 200?)≈ 5– 32 cm, narrowly elliptic in outline, middle pinnae adnate at base, lowest pinnae of sterile fronds reduced to auricles, middle pinnae acuminate at apex, decurrent at base, longest sterile pinnae 40– 210≈ 8– 19 mm, very narrowly triangular-oblong to linear, margin entire, sometimes falcate, longest fertile pinnae linear, 30– 180≈ 2– 4 mm. Sori extending along most of fertile pinnae, unbroken, indusium entire to slightly erose, 0.4– 0.6 mm wide. Fig. 1/1, 5 (p. 3).
Range
DISTR. U 2; K 3– 5, 7; T 2, 3, 6– 8
Altitude range
1500– 3000 m
Distribution
UGANDA Toro District Ruwenzori, R. Nyamugasani, 22 Aug. 1952, Osmaston 2191! & Ruwenzori, Wimi, Scott Elliot 7882!;KENYA Meru District volcanic cone Kirui, E slope of Mt Kenya, 13 April 1969, Faden et al. 69/497!;TANZANIA Arusha District Mt Meru, Engare Nanyuki R., 3 March 1971, Richards 26831!;UGANDA Kigezi District Impenetrable Forest, Sept. 1936, Eggeling 3252!KENYA Kericho District SW Mau Forest, along the Kiptiget [Chepkoisi] R. ±16 km SSE of Kericho, 12 June 1972, Faden et al. 72/345!;KENYA Teita District Kasigau, Rukanga route, 16 Nov. 1994, Luke & Luke 4124!TANZANIA Lushoto District W Usambaras, Mbalamu, Shagai forest, 15 March 1893, Holst 2479!;TANZANIA Morogoro District Ngata River above Huala Falls, 24 Aug. 1951, Greenway & Eggeling 8864!
Distribution (external)
; Cameroon
Bioko
São Tomé
Zambia
Malawi
Zimbabwe
Comoro Islands
Réunion
Mauritius
Madagascar
Notes
Schelpe (J. Linn. Soc. Bot. 53: 493, 1952) cites the type of B. attenuatum (Sw.) Mett. var. holstii (Hieron.) Schelpe as being in K. Material of the type number, Holst 2479, at K and B belongs to a small form of B. attenuatum, but other material of this collection at B and at P is referable to B. ivohibense. One sheet at B bears the label ‘ Blechnum Holstii Hieron. steht dem B. polypodioides nahe. Det. Georg Hieronymus’. As this is the only sheet seen that has been annotated by Hieron. it is selected as the lectotype of var. holstii (see under B. ivohibense ). Blechnum attenuatum is very variable in our area in habit, thickness of rhizome and colour of rhizome scales. Fronds of juvenile plants have a long undivided lamina apex. Blechnum giganteum (Kaulf.) Schltdl. is a closely related Southern African species to which some East African material has been referred (Johns, Pterid. T.E.A.: 98, 1991). It has been distinguished from B. attenuatum by its larger size and terrestrial or lithophytic, rather than epiphytic (rarely lithophytic), habit, and rhizome 20– 34 mm in diameter, rather than less than 20 mm in diameter. (Burrows, S. Afr. Ferns & Fern Allies: 326, 1990; Jacobsen, Ferns S. Afr.: 460, 1983; F.S.A. Pteridophyta, 269, 1986). Chambers (annotations on various herbarium sheets at K), seems to regard bicolorous scales as indicative of B. attenuatum and concolorous scales as characteristic of B. giganteum, but I have seen concolorous scales on plants of epiphytic habit with slender rhizomes and small fronds that are otherwise clearly referable to B. attenuatum. Plants may also have both concolorous and bicolorous scales. It is impossible to distinguish two species in East African material using the characters mentioned above because of the degree of intergradation between them. A form of B. attenuatum with very small fronds widely spaced on a slender creeping rhizome was distinguished by Schelpe (J. L.S. Bot. 53: 493, 1952) as var. holstii, but this name is a synonym of B. ivohibense (q. v.). This form merits further study in the context of variation within and between B. attenuatum and B. giganteum .

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